1. Field of the Invention
This invention relates to an apparatus and process for aluminothermic welding without preheating of metal parts, with rising channels and central part of welding cavity controlling such process and with ventilating means for entirely eliminating of gases.
2. Prior Art
In aluminothermic welding without preheating of two or more identical or similar metal parts of variable cross-sections, such as rails, aligned in an end-to-end relation, several methods are known in which the amount of heat required to weld the rail ends is supplied solely by the liquid steel aluminothermically produced.
However, no method is known in which the stress applied to the weld head is decreased by increasing the moment of inertia of cross-section of weld and by increasing the height between the weld base and the neutral axis of weld while the moment of fatigue of weld base and the moment of fatigue of weld head are so balanced as to obtain an increase of the endurance of the resulted weld.
At the same time, a single method is known in which the area of the cross-section of a rising channel varies along said channel in such a manner that areas in the longitudinal section of different portions of a channel are proportional to areas of corresponding portions of rail.
In one such process and apparatus, described in Romania Pat. No. 80,214, the rail ends are positioned with a gap therebetween and enclosed in a welding mold, which contains stepped rising channels, connecting gates and ventilating ducts. After a casting crucible is manually tapped, a single liquid stream flows into the welding cavity centrally through the gap and fills the welding cavity and the rising channels. However, this method is subject to several disadvantages. Because the two cores used in employing the rising channels are in an interdependent relation, the rising channels are not sufficiently large in the region of rail head, and the rail head would not be properly melted. Also, technical difficulties are encountered when the stepped rising channels are to be employed with inter-dependent cores. This method requires large spaces around metal parts for eliminating of gases from the base portion and the web portion of welding cavity during the pouring operation, such that this method does not employ a weld without rib and further finishing in the region of weld web is required.
No such welding apparatus and method without preheating of rails is known in which the space around the metal parts in the region of web portion of the welding cavity is sufficiently narrow, such that a weld without rib on the sides of weld web is not employed without further finishing in the region of weld.